The objective of the proposed study is to understand the oncogenic role of MUC1 glycoprotein in the development and progression of infiltrating ductal adenocarcinoma of the pancreas (PDA) from preinvasive neoplasias (PanlNs) to invasive adenocarcinomas, and to evaluate the efficacy of MUC1-targeted therapeutic intervention for the treatment and/or prevention of this devastating disease. MUC1 (CD227) is a membrane tethered mucin glycoprotein overexpressed and aberrantly glycosylated in >60% of human ductal pancreatic adenocarcinoma. Tumor-associated MUC1 is known to be associated with the metastatic phenotype of cancer cells. MUC1 is recently identified as a potential oncogene, and has been an active target for therapeutic intervention in several cancers including PDA. Over expression of MUC1 in PDA has long been known, but its function has been difficult to elucidate, partly due to the lack of appropriate models. With the advent of siRNA technology and the recent development of a mouse model of PDA, we can begin to fully elucidate the role of MUC1. Our hypothesis is that MUC1 plays an important oncogenic function in pancreatic cancer development and serves as a target for therapeutic intervention. Our specific aims are 1) To determine the functional role of MUC1 in human pancreatic cancer cell lines;2) To determine the effects on the development of PanlNs and PDA in Mud -deficient PDA mice;and 3) To evaluate the effects on the development of PanlNs and PDA in PDA mice expressing human MUC1. These mouse models provide an unique and distinctive opportunity to not only understand the role of MUC1 during pancreatic cancer development, but also offers us the ability to evaluate MUC1-targeted immune therapy in the PDA mice that expresses human MUC1 as a self-antigen. In the third aim we also propose to determine novel strategies to reduce tumor-induced immune-suppression within the tumor microenvironment to improve efficacy of targeted immune therapy. This project is extremely relevant to pancreatic cancer. These preclinical studies will form the basis for designing more efficacious and novel therapies to combat the mortality associated with PDA.